Aside from the Trauttmansdorff Castle Gardens and the Therme, what else in Merano is worth a view? We'll be there for only two days.
I really enjoyed walking the Promenades along the Passer River. Edited to add that I got to the Gardens at Trauttmansdorf Castle by walking the Sissi-Weg trail (some of which does have car traffic), which goes through vineyards and apple orchards, and has beautiful views.
These are the flat hill walks through the orchards and vineyards which surround Merano. They are gently sloping water channels.
https://www.meranerland.org/en/leisure-activities/mountains-and-hiking/waalweg-paths/